Meta-Structure Hull Design with Periodic Layered Phononic Crystals Theory for Wide-Band Low-Frequency Sound Insolation

Abstract

The hulls of marine vehicles are generally very effective at attenuating airborne acoustic noise generated by their powertrains. However, conventional hull designs are generally not very effective at attenuating wide-band low-frequency noise. Meta-structure concepts offer an opportunity for the design of laminated hull structures tailored to address this concern. This research proposes a novel meta-structure laminar hull concept using periodic layered Phononic crystals to optimize the sound insolation performance on the air–solid side of the hull structure. The acoustic transmission performance is evaluated using the transfer matrix, the acoustic transmittance, and the tunneling frequencies. The theoretical and numerical models for a proposed thin solid-air sandwiched meta-structure hull indicate ultra-low transmission within a 50-to-800 Hz frequency band and with two predicted sharp tunneling peaks. The corresponding 3D-printed sample experimentally validates the tunneling peaks at 189 Hz and 538 Hz, with 0.38 and 0.56 transmission magnitudes, respectively, with the frequency band between those values showing wide-band mitigation. The simplicity of this meta-structure design provides a convenient way to achieve acoustic band filtering of low frequencies for marine engineering equipment and, accordingly, an effective technique for low-frequency acoustic mitigation.

Broadband Waterborne Multiphase Pentamode Metastructure with Simultaneous Wavefront Manipulation and Energy Absorption Capabilities

“…Inspired by this mechanism and introducing the viscoelasticity of the substrate, strong low-frequency waterborne absorption is realized by Wen et al with a sub-wavelength sample [ 4 ], but the inferiority of this is that the effective frequency bandwidth is very narrow. A lot of studies have been conducted to expand the effective frequency bandwidth by introducing multi-resonators [ 5 , 6 , 7 , 8 , 9 ], metal spiral and inter-connecting structures [ 10 , 11 , 12 ], air cavities and combinations of them [ 13 , 14 , 15 , 16 , 17 ]. For example, Wang et al proposed a broadband waterborne absorbing metamaterial with gradient cavity array strengthened by a carbon fiber framework [ 15 ].…”

Broadband Waterborne Multiphase Metasurface with Simultaneous Wavefront Manipulation and Energy Absorption

“…Inspired by this mechanism and introducing viscoelasticity of substrate, low frequency waterborne strong absorption is realized by Wen et al with a sub-wavelength sample [4], but the inferiority is that the effective frequency bandwidth is very narrow. A lot of studies have been done to expand the effective frequency bandwidth by introducing multi-resonators [5][6][7][8][9], metal spiral and inter-connecting structures [10][11][12], air cavities and combinations of them [13][14][15][16][17]. For example, combining two absorption mechanisms of cavity resonance and impedance transition loss, 3 polymer (E≈1GPa) whose damping coefficient is very small is adopted and the damping of the substrates and structures is ignored.…”